[Role of bcl-2 and bax expression in apoptosis of hypoxic pulmonary artery smooth muscle cells of rats induced by Na+/H+ exchanger isoform-1 inhibition in vitro].

OBJECTIVE: To investigate the role of bcl-2 and bax expression in apoptosis of hypoxic pulmonary artery smooth muscle cells (PASMCs) of rats induced by Na+/H+ exchanger isoform-1 (NHE-1) inhibition in vitro. METHODS: Cultured rat PASMCs transfected with NHE-1 ribozyme gene (PRZ cell), cultured rat PASMCs transfected only with pLXSN vector (PX cell) and non-transfected rat PASMCs (PA cell) were obtained in our previous studies. The cells were cultured under low oxygen tension (<1% O2) for 0, 2, 6, 12, 24 and 48 hours respectively. Then cell apoptosis was examined with terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL). Intracellular Ca2+([Ca2+]i) of cells was measured using fluorescence dye Fura-2/AM. The changes in mRNA expression of bcl-2 and bax in cells were assessed by semi quantitative reverse transcription-polymerase chain reaction (sqRT-PCR). The expression of Bcl-2 protein and Bax protein of cells was detected immunohistochemically. RESULTS: In contrast to normal PASMCs and cells transfected with pLXSN, the apoptosis rates in recombinant vectors transfected cells increased significantly and continuously. [Ca2+]i values were also increased in these cells, but the increase extent was remarkably lower than in the normal PASMCs (all P<0.01). The expression of bax mRNA and protein of cells transfected with recombinant vectors was increased significantly compared with cells of other two groups. Meanwhile, the expression of bcl-2 mRNA and protein of these cells were decreased significantly. CONCLUSION: The NHE-1 specific hammerhead ribozymes induce apoptosis of PASMCs under low oxygen tension by inhibiting the increase in intracellular Ca2+ concentration, increasing bax expression and decreasing bcl-2 expression.